Liquid sample measurement method and apparatus

ABSTRACT

A liquid sample measurement apparatus of the present invention is provided with a timer ( 122 ) for measuring the time from when a biosensor ( 30 ) is attached to a liquid sample measurement device ( 110   a ) which measures the concentration of a specific component in a liquid sample that is applied to the biosensor ( 30 ) to when the liquid sample is applied to the biosensor ( 30 ), and correction based on the time measured by the timer ( 122 ) is performed to the measurement result of the concentration of the specific component in the liquid sample that is applied to the biosensor ( 30 ). Thereby, the measurement precision can be enhanced with utilizing the correction algorithm in which the ambient temperature and the temperature of the biosensor itself are considered.

TECHNICAL FIELD

The present invention relates to liquid sample measurement method andapparatus for determining the quantity of a specific component in aliquid sample using a biosensor.

BACKGROUND ART

A biosensor is a sensor which applies a biological material to amolecule identification element by utilizing a molecule recognitionability of the biological material such as a micro-organism, an enzyme,or an antibody. To be specific, the biosensor utilizes a reaction whichoccurs when an immobilized biological material recognizes a targetspecific component, consumption of oxygen by respiration of amicro-organism, an enzyme reaction, luminescence or the like.Especially, practical use of a biosensor utilizing an enzyme reactionhas been progressed, and it is utilized in the medical field and thefood field.

Hereinafter, an example of a biosensor measurement system utilizing anenzyme reaction will be described with reference to FIG. 13.

A biosensor measurement system 20 includes a biosensor 30 having asample application part 30 a at its front end, and a measurement unit 21which measures the concentration of a specific component in a liquidsample that is applied to the sample application part 30 a.

The measurement unit 21 includes a display part 22 which displays themeasurement result, and a support part 23 in which the biosensor 30 isinserted.

The biosensor 30 is obtained by laminating a cover 31, a spacer 33, areagent layer 35, and an insulating substrate 36 as shown in FIG. 14.The cover 31 has an vent hole 32 in its center. The spacer 33 has anapproximately rectangular sample supply channel 34. The reagent layer 35supports a reagent which enzymatically reacts with the specificcomponent in the liquid sample. The insulating substrate 36 comprisespolyethylene terephthalate or the like, and an electrode layer is formedat its surface. The electrode layer is divided by a laser or the like,thereby forming a working electrode 37, a detection electrode 38, and acounter electrode 39.

Next, a liquid sample measurement method by the biosensor measurementsystem 20 will be described. The description will be given of a case ofmeasuring the glucose concentration in blood.

When the biosensor 30 is inserted in the support part 23 of themeasurement unit 21, a constant voltage is applied between the workingelectrode 37 and the counter electrode 39.

When blood is applied to the sample application part 30 a of thebiosensor 30, the blood penetrates along the sample supply channel 34 bycapillary phenomenon to reach the reagent layer 35, and then an enzymereaction occurs between glucose in the blood and the reagent supportedby the reagent layer 35. A change in current between the workingelectrode 37 and the counter electrode 39 which occurs upon the enzymereaction is detected. Then, the glucose concentration in the blood iscalculated based on the detected current change value, and thecalculation result is displayed on the display part 22 of themeasurement unit 21.

By the way, since the enzyme reaction has a large temperaturedependence, the measurement precision is degraded due to a temperaturechange or the like during the measurement.

So, in order to improve the measurement precision, there has beenproposed a biosensor measurement system in which a measurement apparatusis provided with a temperature correction algorithm for correcting themeasurement result according to the ambient temperature during themeasurement by using a temperature correction table which shows therelations between prepared glucose concentrations and temperaturecorrection amounts (Patent Document 1).

Furthermore, as biosensor measurement systems for improving themeasurement precision, there have been proposed a biosensor measurementsystem which measures the temperature of the biosensor itself with athermal conductive layer provided on the insulating substrate 36 of thebiosensor 30, and corrects the measurement result on the basis of thetemperature of the biosensor itself (Patent Documents 2 and 3), and abiosensor measurement system having a temperature detector at thesupport part 23 of the measurement device 21, which measures thetemperature of the biosensor 30 itself by bringing the biosensor 30inserted in the support part 23 in contact with the temperaturedetector, and corrects the measurement result on the basis of thetemperature of the biosensor itself (Patent Document 4).

Patent Document 1: Japanese Unexamined Patent Publication No. Hei.8-503304

Patent Document 2: Japanese Published Patent Application No. 2001-235444

Patent Document 3: Japanese Published Patent Application No. 2003-42995

Patent Document 4: International Publication No. 2003/062812

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The temperature correction algorithm installed in the conventionalbiosensor measurement system as disclosed in Patent Document 1 does notmeasure the temperature of an actual sample but measures the ambienttemperature surrounding the measurement device and regards this value asthe temperature of the sample. However, the biosensors which arecommonly used at present are mostly handled with bare hands of users,and the heat of the finger tips of the user is conducted to thebiosensor to locally change the temperature of the biosensor, andthereby the actual sample temperature might differ from the ambienttemperature. Especially in self blood glucose measurement systems fordiabetic patients, the user inserts the sensor into the measurement unitdirectly with his hand. In recent years, such self blood glucosemeasurement sensors have been advanced in miniaturization, and most ofthem are configured such that the user's hand touches the vicinity ofthe reagent reaction part when the user inserts the sensor into themeasurement unit. If measurement is started in such state, since thesurrounding ambient temperature read by a thermistor of the measurementdevice differs from the sample temperature, appropriate correctioncannot be performed and a value that is significantly deviated from thetrue value is undesirably indicated. It is supposed that such problemfrequently occurs especially when the analyte measurement is performedimmediately after the insertion of the biosensor into the measurementdevice, for example, when a nurse or an operator measures the analyte ofa patient or when a parent having a diabetic child helps themeasurement, and it is one of major challenges to further improve themeasurement precision.

On the other hand, although the biosensor measurement system proposed inPatent Document 2 or 3 can gain the temperature of the biosensor itself,since the biosensor itself must be provided with the thermistor, thebiosensor becomes expensive, and therefore, it is not practical when thebiosensor is disposable. Further, since such biosensor measurementsystem depends on temperature measurement by the thermal conductivelayer, it is poor in reproducibility and requires a long measurementtime.

Furthermore, since the biosensor measurement system proposed in PatentDocument 4 requires the temperature detector provided in the measurementdevice, the cost is increased and the measurement precision might bedeteriorated when the measurement time is short.

Moreover, the measurement time tends to be reduced in recent biosensormeasurement systems. For example, in blood glucose measurement,measurement is completed in about five seconds after blood is applied tothe sensor. Therefore, the influences of not only the surroundingambient temperature but also the actual temperature of the reaction parton the measurement result are increased, and a biosensor measurementsystem of higher measurement precision is desired.

The present invention is made to solve the above-described problems andhas for its object to provide a method and an apparatus for measuring aliquid sample, which can reduce measurement errors with a simpleconfiguration while considering the influence of temperature on themeasurement precision.

Measures to Solve the Problems

In order to solve the above-described problems, there is provided aliquid sample measurement method of attaching a biosensor to ameasurement device and measuring the concentration of a specificcomponent in a liquid sample that is applied to the biosensor, whichmethod includes the steps of measuring the time from when the biosensoris attached to the measurement device to when the liquid sample isapplied to the sensor; and performing correction for the measurementresult of the concentration of the specific component in the liquidsample that is applied to the biosensor, on the basis of the measuredtime.

According to claim 2 of the present invention, there is provided aliquid sample measurement method of attaching a biosensor to ameasurement device and measuring the concentrations of plural specificcomponents in a liquid sample that is applied to the biosensor, whichmethod includes the steps of measuring the time from when the biosensoris attached to the measurement device to when the liquid sample isapplied to the sensor; and performing corrections for the respectivemeasurement results of the concentrations of the plural specificcomponents in the liquid sample that is applied to the biosensor, on thebasis of the measured time.

According to claim 3 of the present invention, there is provided aliquid sample measurement method of attaching plural biosensors ofdifferent types to a measurement device and measuring the concentrationsof specific components in liquid samples that are applied to therespective biosensors, which method includes the steps of measuring thetime from when each of the biosensors is attached to the measurementdevice to when the liquid sample is applied to the sensor; andperforming correction for the measurement result of the concentration ofthe specific component in the liquid sample that is applied to thebiosensor, on the basis of the measured time and the type of thebiosensor.

According to claim 4 of the present invention, in the liquid samplemeasurement method defined in any of claims 1 to 3, the amount ofcorrection for the measurement result of the concentration of thespecific component in the liquid sample that is applied to the biosensoris varied according to the measured time from when the biosensor isattached to the measurement device to when the liquid sample is appliedto the sensor.

According to claim 5 of the present invention, in the liquid samplemeasurement method defined in claim 4, the amount of correction isreduced when the measured time from when the biosensor is attached tothe measurement device to when the liquid sample is applied to thesensor is long.

According to claim 6 of the present invention, in the liquid samplemeasurement method defined in any of claims 1 to 3, whether correctionshould be performed or not for the measurement result of theconcentration of the specific component in the liquid sample that isapplied to the biosensor is judged according to the measured time fromwhen the biosensor is attached to the measurement device to when theliquid sample is applied to the sensor.

According to claim 7 of the present invention, in the liquid samplemeasurement method defined in claim 6, the correction is performed whenthe measured time from when the biosensor is attached to the measurementdevice to when the liquid sample is applied to the sensor is within aspecific time period.

According to claim 8 of the present invention, in the liquid samplemeasurement method defined in any of claims 1 to 3, the amount ofcorrection for the measurement result is determined according to themeasurement result of the concentration of the specific component in theliquid sample that is applied to the biosensor.

According to claim 9 of the present invention, in the liquid samplemeasurement method defined in any of claims 1 to 3, the amount ofcorrection for the measurement result of the concentration of thespecific component in the liquid sample that is applied to the biosensoris determined according to the ambient temperature at the measurement.

According to claim 10 of the present invention, in the liquid samplemeasurement method defined in any of claims 1 to 3, the amount ofcorrection for the measurement result of the concentration of thespecific component in the liquid sample that is applied to the biosensoris determined according to a second specific component which exists inthe liquid sample and is other than said specific component.

According to claim 11 of the present invention, in the liquid samplemeasurement method defined in claim 10, the liquid sample is blood, andthe amount of correction is determined according to the hematocrit valueof the blood.

According to claim 12 of the present invention, there is provided aliquid sample measurement method of attaching a biosensor to ameasurement device and measuring the concentration of a specificcomponent of a liquid sample that is applied to the sensor, which methodincludes the steps of measuring the time from when the biosensor isattached to the measurement device to when the liquid sample is appliedto the sensor, and the ambient temperature at the measurement;correcting the measured ambient temperature on the basis of the measuredtime from when the biosensor is attached to the measurement device towhen the liquid sample is applied to the sensor; and correcting themeasurement result of the concentration of the specific component in theliquid sample that is applied to the biosensor, on the basis of thecorrected ambient temperature.

According to claim 13 of the present invention, in the liquid samplemeasurement method defined in any of claims 1 to 3, the amount ofcorrection for the measurement result is determined according to thekind of the liquid sample that is applied to the biosensor.

According to claim 14 of the present invention, there is provided aliquid sample measurement apparatus having a biosensor attached thereto,which measures the concentration of a specific component in a liquidsample that is applied to the biosensor, including: a time measurementmeans for measuring the time from when the biosensor is attached to whenthe liquid sample is applied to the sensor; and a measurement resultcorrection means for correcting the measurement result of theconcentration of the specific component in the liquid sample that isapplied to the biosensor, on the basis of the time measured by the timemeasurement means.

According to claim 15 of the present invention, in the liquid samplemeasurement apparatus defined in claim 14, the measurement resultcorrection means changes the amount of correction for the measurementresult of the concentration of the specific component in the liquidsample that is applied to the biosensor, according to the time measuredby the time measurement means.

According to claim 16 of the present invention, in the liquid samplemeasurement apparatus defined in claim 15, the measurement resultcorrection means reduces the amount of correction when the time measuredby the time measurement means is long.

According to claim 17 of the present invention, in the liquid samplemeasurement apparatus defined in claim 14, the measurement resultcorrection means judges whether correction should be performed or notfor the measurement result of the concentration of the specificcomponent in the liquid sample that is applied to the biosensor,according to the time measured by the time measurement means.

According to claim 18 of the present invention, in the liquid samplemeasurement apparatus defined in claim 17, the measurement resultcorrection means performs said correction when the time measured by thetime measurement means is within a specific time.

According to claim 19 of the present invention, in the liquid samplemeasurement apparatus defined in claim 14, the measurement resultcorrection means determines the amount of correction for the measurementresult according to the measurement result of the concentration of thespecific component in the liquid sample that is applied to thebiosensor.

According to claim 20 of the present invention, the liquid samplemeasurement apparatus defined in claim 14 further includes a temperaturemeasurement part for measuring the ambient temperature at themeasurement, and the measurement result correction means determines theamount of correction for the measurement result of the concentration ofthe specific component in the liquid sample that is applied to thebiosensor, according to the ambient temperature measured by thetemperature measurement part.

According to claim 21 of the present invention, in the liquid samplemeasurement apparatus defined in claim 14, the measurement resultcorrection means determines the amount of correction for the measurementresult of the concentration of the specific component in the liquidsample that is applied to the biosensor, according to a second specificcomponent which exists in the liquid sample and is other than saidspecific component.

According to claim 22 of the present invention, in the liquid samplemeasurement apparatus defined in claim 21, the liquid sample is blood,and the second specific component is the hematocrit value of the blood.

According to claim 23 of the present invention, in the liquid samplemeasurement apparatus defined in claim 14, the measurement resultcorrection means determines the amount of correction for the measurementresult according to the type of the liquid sample that is applied to thebiosensor.

According to claim 24 of the present invention, there is provided aliquid sample measurement apparatus having a biosensor attached thereto,which measures the concentration of a specific component in a liquidsample that is applied to the biosensor, including: a time measurementmeans for measuring the time from when the biosensor is attached to whenthe liquid sample is applied to the sensor; a temperature sensor formeasuring the ambient temperature at measurement; a temperaturecorrection means for correcting the ambient temperature measured by thetemperature sensor, on the basis of the time measured by the timemeasurement means; and a measurement result correction means forperforming correction for the measurement result of the concentration ofthe specific component in the liquid sample that is applied to thebiosensor, on the basis of the corrected ambient temperature.

EFFECTS OF THE INVENTION

According to the present invention, in a liquid sample measurementmethod of attaching a biosensor to a measurement device and measuringthe concentration of a specific component in a liquid sample that isapplied to the sensor, the time from when the biosensor is attached tothe measurement device to when the liquid sample is applied to thesensor is measured, and the measurement result of the concentration ofthe specific component in the liquid sample that is applied to thebiosensor is corrected based on the measured time. Therefore, whenmeasuring the concentration of the specific component in the liquidsample, the ambient temperature and the temperature of the sensor itselfare prevented from adversely affecting the measurement result, therebyobtaining a highly-precise measurement result when the measurement timeis short.

Further, according to the present invention, in a liquid samplemeasurement method of attaching a biosensor to a measurement device andmeasuring the concentrations of plural specific components in a liquidsample that is applied to the biosensor, the time from when thebiosensor is attached to the measurement device to when the liquidsample is applied to the sensor is measured, and the measurement resultsof the concentrations of the plural specific components in the liquidsample that is applied to the biosensor are respectively corrected basedon the measured time. Therefore, when measuring the concentration of thespecific component in the liquid sample, the ambient temperature and thetemperature of the sensor itself are prevented from adversely affectingthe measurement result, thereby obtaining a highly-precise measurementresult when the measurement time is short.

Further, according to the present invention, in a liquid samplemeasurement method of attaching plural biosensors of different types toa measurement device and measuring the concentrations of specificcomponents in liquid samples that are applied to the respectivebiosensors, the time from when each of the biosensors is attached to themeasurement device to when the liquid sample is applied to the sensor ismeasured, and the measurement result of the concentration of thespecific component in the liquid sample that is applied to the biosensoris corrected based on the measured time and the type of the biosensor.Therefore, when measuring the concentration of the specific component inthe liquid sample, the ambient temperature and the temperature of thesensor itself are prevented from adversely affecting the measurementresult, thereby obtaining a highly-precise measurement result when themeasurement time is short.

Further, according to the present invention, in a liquid samplemeasurement method of attaching a biosensor to a measurement device andmeasuring the concentration of a specific component of a liquid samplethat is applied to the sensor, the time from when the biosensor isattached to the measurement device to when the liquid sample is appliedto the sensor and the ambient temperature at the measurement aremeasured, the measured ambient temperature is corrected based on themeasured time from when the biosensor is attached to the measurementdevice to when the liquid sample is applied to the sensor, and themeasurement result of the concentration of the specific component in theliquid sample that is applied to the biosensor is corrected based on thecorrected ambient temperature. Therefore, when measuring theconcentration of the specific component in the liquid sample, theambient temperature and the temperature of the sensor itself areprevented from adversely affecting the measurement result, therebyobtaining a highly-precise measurement result when the measurement timeis short.

Further, according to the present invention, a liquid sample measurementapparatus having a biosensor attached thereto, which measures theconcentration of a specific component in a liquid sample that is appliedto the biosensor, includes a time measurement means for measuring thetime from when the biosensor is attached to when the liquid sample isapplied to the sensor, and a measurement result correction means forcorrecting the measurement result of the concentration of the specificcomponent in the liquid sample that is applied to the biosensor, on thebasis of the time measured by the time measurement means. Therefore,when measuring the concentration of the specific component in the liquidsample, the ambient temperature and the temperature of the sensor itselfare prevented from adversely affecting the measurement result, therebyrealizing an apparatus which can improve the measurement precision evenwhen the measurement time is short.

Further, according to the present invention, a liquid sample measurementapparatus having a biosensor attached thereto, which measures theconcentration of a specific component in a liquid sample that is appliedto the biosensor, includes a time measurement means for measuring thetime from when the biosensor is attached to when the liquid sample isapplied to the sensor, a temperature sensor for measuring the ambienttemperature at measurement, a temperature correction means forcorrecting the ambient temperature measured by the temperature sensor,on the basis of the time measured by the time measurement means, and ameasurement result correction means for performing correction for themeasurement result of the concentration of the specific component in theliquid sample that is applied to the biosensor, on the basis of thecorrected ambient temperature. Therefore, when measuring theconcentration of the specific component in the liquid sample, theambient temperature and the temperature of the sensor itself areprevented from adversely affecting the measurement result, therebyrealizing an apparatus which can improve the measurement precision evenwhen the measurement time is short.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of configuration of abiosensor measurement system according to a first embodiment of thepresent invention.

FIG. 2 is a diagram illustrating a liquid sample measurement method bythe biosensor measurement system of the first embodiment.

FIG. 3( a) is a graph illustrating sensor response values obtained whenusing the conventional biosensor measurement system, and FIG. 3( b) is agraph illustrating sensor response values obtained when using thebiosensor measurement system of the first embodiment.

FIG. 4 is a diagram illustrating examples of correction tables which areused when performing correction to the measurement result ofconcentration of a specific component in an analyte that is applied tothe biosensor in the biosensor measurement system of the firstembodiment.

FIG. 5 is a diagram illustrating an example of a correction table whichis used when performing correction to the measurement result ofconcentration of a specific component in blood as an analyte that isapplied to the biosensor in the biosensor measurement system of thefirst embodiment.

FIG. 6 is a diagram illustrating a liquid sample measurement method by abiosensor measurement system according to a second embodiment of thepresent invention.

FIG. 7 is a diagram illustrating an example of configuration of abiosensor measurement system according to a third embodiment of thepresent invention.

FIG. 8 is an exploded perspective view illustrating an example ofconfiguration of the biosensor in the biosensor measurement system ofthe third embodiment.

FIG. 9 is a diagram illustrating a liquid sample measurement method bythe biosensor measurement system of the third embodiment.

FIG. 10 is a diagram illustrating examples of correction tables to beused when correcting the measurement result of lactic acid concentrationin an analyte that is applied to the biosensor in the biosensormeasurement system of the third embodiment.

FIG. 11( a) is a graph illustrating glucose response values obtainedwhen the conventional biosensor measurement system is used, and FIG. 11(b) is a graph illustrating the lactic acid response-values obtained whenthe conventional biosensor measurement system is used.

FIG. 12( a) is a graph illustrating glucose response values obtainedwhen the biosensor measurement system of the third embodiment is used,and FIG. 12( b) is a graph illustrating the lactic acid response valuesobtained when the biosensor measurement system of the third embodimentis used.

FIG. 13 is a diagram illustrating an example of the conventionalbiosensor measurement system.

FIG. 14 is an exploded perspective view illustrating an example ofconfiguration of a biosensor.

DESCRIPTION OF REFERENCE NUMERALS

-   -   20 . . . biosensor measurement system    -   21 . . . measurement device    -   22 . . . display part    -   23 . . . support part    -   30 . . . biosensor    -   30 a . . . sample application part    -   31 . . . cover    -   32 . . . vent hole    -   33 . . . spacer    -   34 . . . sample supply channel    -   35 . . . reagent layer    -   36 . . . insulating substrate    -   37 . . . working electrode    -   38 . . . detection electrode    -   39 . . . counter electrode    -   100 a, 100 b . . . biosensor measurement system    -   110 a, 110 b . . . measurement device    -   112, 113, 114, 123, 124, 125, 126, 127 . . . connector    -   115 . . . switching circuit    -   116 . . . current/voltage conversion circuit    -   117 . . . A/D conversion circuit    -   118 . . . CPU    -   119 . . . reference voltage supply    -   120 . . . thermistor    -   121 . . . RAM    -   122 . . . timer    -   700 . . . biosensor    -   700 a . . . sample application part    -   701 . . . cover    -   702 . . . vent hole    -   703 . . . spacer    -   704 . . . sample supply channel    -   705 . . . reagent layer for lactic acid measurement    -   706 . . . reagent layer for glucose measurement    -   707 . . . working electrode for lactic acid measurement    -   708 . . . working electrode for glucose measurement    -   709 . . . detection electrode    -   710 . . . counter electrode for glucose measurement    -   711 . . . counter electrode for lactic acid measurement    -   712 . . . insulating substrate

BEST MODE TO CARRY OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the drawings.

Embodiment 1

Hereinafter, a biosensor measurement system according to a firstembodiment of the present invention will be described. In thisembodiment, blood is used as an analyte.

FIG. 1 is a diagram illustrating the configuration of the biosensormeasurement system of the first embodiment.

The biosensor measurement system 100 a of the first embodiment isprovided with a biosensor 30 and a measurement device 110 a. Theexterior appearance of the biosensor measurement system 100 a isidentical to the conventional one shown in FIG. 13, and the measurementdevice 110 a is provided with a display part for displaying themeasurement result, and a support part in which the biosensor isinserted.

As shown in FIG. 14, the biosensor 30 is obtained by laminating a cover31, a spacer 33, a reagent layer 35, and an insulating substrate 36. Thecover 31 has an vent hole 32 in its center. The spacer 33 has anapproximately rectangle-shaped sample supply channel 34. The reagentlayer 35 supports a reagent which enzymatically reacts with a specificcomponent in a liquid sample. The insulating substrate 36 comprisespolyethylene terephthalate or the like, and an electrode layer is formedat its surface. The electrode layer is divided to a working electrode37, a detection electrode 38, and a counter electrode 39 by a laser orthe like.

The measurement device 110 a is provided with a display part 111,connectors 112, 113, and 114, a switching circuit 115, a current/voltageconversion circuit 116, an A/D conversion circuit 117, a CPU 118, areference voltage supply 119, a temperature sensor 120, a RAM 121, and atime measurement means (timer) 122.

The connectors 112, 113, and 114 contact the working electrode 37, thedetection electrode 38, and the counter electrode 39 of the biosensor30, respectively. The switching circuit 115 switches the connectionsbetween the connectors 112 to 114 and the reference voltage supply 119and the connections between the connectors 112 to 114 and thecurrent/voltage conversion circuit 116. The current/voltage conversioncircuit 116 converts a current that flows between the working electrode37 and the other electrodes 38 and 39 into a voltage. The A/D conversioncircuit 117 converts an output value from the current/voltage conversioncircuit 116 into a pulse. The CPU 118 calculates the concentration ofthe specific component in the liquid sample on the basis of the pulsefrom the A/D conversion circuit 117. The reference voltage supply 119applies a voltage to the connectors 112 to 114. The temperature sensor120 measures the temperature of the measurement environment. The timer122 measures the time required from when the biosensor 30 is inserted inthe support part of the measurement device 11 a to when the liquidsample is applied to the sensor 30. The RAM 121 stores a temperaturecorrection table (not shown) for determining the amount of correctionfor the measurement result of the concentration of the specificcomponent in the liquid sample applied to the biosensor 30 on the basisof the ambient temperature, and a correction table (refer to FIGS. 3 and4) for determining the amount of correction for the measurement resultof the concentration of the specific component in the liquid sampleapplied to the biosensor 30 on the basis of the time from when thebiosensor 30 is set in the measurement device 110 a to when introductionof the analyte is detected. A ROM may be used to store the correctiontables.

Hereinafter, the features of the biosensor measurement system 100 a ofthe first embodiment will be described in comparison with theconventional one.

Although the conventional biosensor measurement system 20 previouslystores the temperature correction table showing the correction amountsbased on the glucose concentration and the ambient temperature into themeasurement device 21 to perform temperature correction using thetemperature correction table for the measurement result of the glucoseconcentration in the blood that is applied to the biosensor 30, thefollowing drawbacks have occurred according to the time up to the startof measurement.

FIG. 3( a) shows the measurement result obtained by the conventionalbiosensor measurement system 20. The abscissa shows the time T(sec) fromwhen the biosensor 30 is inserted in the measurement device 21 to whenblood is applied to the sensor 30, and the ordinate shows the degree ofdivergence (%) from the true value. The measurement was performed at anambient temperature of 25° C., using an analyte which was prepared at aglucose concentration of 100 mg/dl (hematocrit value of 40%). At thistime, the biosensor 30 was inserted in the measurement device 21 by sixdonors having different fingertip temperatures, and the time T until theanalyte was applied to the sensor 30 after insertion of the sensor 30was measured within a range from 0.01 to 30 sec.

As can be seen from FIG. 3( a), the degree of divergence from the truevalue is larger as the time T is shorter. That is, it is considered thatthe fingertip heat influences on the measurement result.

On the other hand, the biosensor measurement system 100 a of this firstembodiment performs correction for the measurement result (thismeasurement result is a value obtained after temperature correction) ofthe glucose concentration in the blood that is applied to the biosensor30 on the basis of the time T from when the biosensor 30 is inserted inthe measurement device 110 a to when the blood is applied to the sensor30.

The amount of correction for the measurement result of the glucoseconcentration in the blood is determined based on the degree ofdivergence from the true value. For example, when time T is 1.0 sec,since the degree of divergence from the true value is +14% as shown inFIG. 3( a), the correction amount in the case where the temperature is25° C. and the glucose concentration is 100 mg/dl is determined at −12%,and correction is performed for the measurement result of the glucoseconcentration in the blood that is applied to the biosensor 30.Likewise, correction is performed for the measurement result with thecorrection amount being set at −9% when the time T is 5.0 sec and withthe correction amount being set at −2% when the time T is 15.0 sec.

Since the measurement result of the glucose concentration in the bloodthat is applied to the biosensor 30 is thus corrected based on the timeT, the degree of divergence from the true value can be minimized evenwhen the time T is within 20 sec as shown in FIG. 3( b), therebyimproving the measurement precision.

Further, in the biosensor measurement system 100 a of this firstembodiment, not only the time T but also the glucose concentration andthe ambient temperature are added as correction parameters as shown inFIG. 4 in order to dramatically improve the measurement precision. Thisis because the influence of the fingertip heat on the measurement resultdiffers depending on the glucose concentration and the ambienttemperature.

FIG. 4( a) is a correction table showing the correction amounts(%) whenthe time T is 1.0 sec, FIG. 4( b) is a correction table showing thecorrection amounts(%) when the time T is 5.0 sec, and FIG. 4( c) is acorrection table showing the correction amounts(%) when the time T is15.0 sec. The ordinate shows the glucose concentration and the abscissashows the temperature. The numerical values on the tables shown in FIG.4 are merely examples, and the correction amounts are not restrictedthereto. Further, the number of tables is also not restricted to thoseshown in FIG. 4, and the measurement precision can be more improved asthe number of tables becomes larger.

Next, the method of calculating the correction amounts using thecorrection tables shown in FIG. 4 will be described.

For example, when the ambient temperature is 25° C., the final responsevalue is 100 mg/dl, and the time T is 1.0 sec, it is found from FIG. 4(a) that the correction amount is −12%. Further, it is found from FIG. 4(b) that the correction amount is −9% when the time T is 5.0 sec, and itis found from FIG. 4( c) that the correction amount is −2% when the timeT is 15.0 sec.

Furthermore, when the time T is 3.0 sec, the correction amount at T=3.0sec is calculated as −10.5% by linearly regressing the correction amount(−12%) at T=1.0 sec and the correction amount (−9%) at T=5.0 sec.

Further, when the liquid sample is blood, the influence of the fingertipheat varies depending on the hematocrit value in the blood. So, acorrection table in which the hematocrit value is newly added as acorrection parameter as shown in FIG. 5 is combined with the correctiontables shown in FIG. 4 to be used for the correction, thereby improvingthe measurement precision. FIG. 5 shows a correction table fordetermining the correction rate from the relation between the hematocritvalue and the glucose concentration. The numerical values on the tableshown in FIG. 5 are merely examples, and the correction amounts are notrestricted thereto. Further, the glucose concentrations and thehematocrit values are also not restricted to those shown in FIG. 5.

While in this first embodiment the hematocrit value is used as thesecond specific component when measuring the glucose concentration,oxidizable substances such as ascorbic acid, uric acid, acetaminophenand the like may be used as the second specific component, and moreover,other predispositions that cause changes in the influence of thefingertip heat may be used as the second specific component.

Next, the liquid sample measurement method by the biosensor measurementsystem 100 a of this first embodiment will be described.

When the biosensor 30 is set in the support part of the measurementdevice 110 a, it is judged by a switch in the support part whether thebiosensor 30 is inserted or not. When it is detected that the biosensor30 is inserted, the power supply of the measurement device 110 a isautomatically turned on (step S201). Then, the ambient temperature ismeasured by the temperature sensor 120 (step S202), and the measurementdevice 110 a goes into the analyte introduction stand-by state (stepS203). The analyte introduction stand-by state is the state afterstarting voltage application from the reference voltage supply 119 tothe connectors 112 to 114, starting current measurement by thecurrent/voltage conversion circuit 116, and starting measurement of timefrom when the biosensor 30 is inserted to when the analyte is applied tothe sensor 30.

While in this first embodiment the power supply of the measurementdevice 110 a is automatically turned on by the insertion of thebiosensor 30, also when the power supply of the measurement device 110 ais manually turned on, it is similarly judged whether the biosensor 30is inserted or not and the measurement device 110 a goes into theanalyte introduction stand-by state. Then, measurement of time from whenthe biosensor 30 is inserted to when the analyte is applied to thesensor 30 is started by the timer 122, thereby obtaining the sameeffect.

When blood as the analyte is applied to the biosensor 30, thecurrent/voltage conversion circuit 116 reads a change in the currentvalue to detect that the analyte is introduced (applied) to the sensor30 (step S204). The count by the timer 122 is completed upon thedetection of the analyte introduction (step S205), and the time T fromwhen the biosensor 30 is inserted in the measurement device 110 a towhen the analyte introduction is detected is calculated (step S206).

Then, the glucose concentration in the blood that is applied to thebiosensor 30 is calculated (step S207). At this time, the correctionamount is obtained from the temperature correction table stored in theRAM 121 on the basis of the ambient temperature measured in step 202,and correction is performed for the measurement result of the glucoseconcentration in the blood that is applied to the biosensor 30.

Thereafter, it is judged based on the time T calculated in step S206 asto whether the glucose concentration value calculated in step S207should be corrected or not (step S208).

As for this judgment, it has previously been set to perform correctionwhen the respective parameters are within the ranges described below.

The time T is set so as to perform correction when it is within a rangefrom 0.01 to 60 sec. Preferably, correction should be performed when thetime T is within a range from 0.01 to 30 sec, and more preferably, from0.01 to 20 sec. The read interval of the time T is set to every 1 sec.Preferably, it is set to every 0.1 sec, and more preferably, every 0.01sec.

The glucose concentration is set so as to perform correction when it iswithin a range from 10 to 800 mg/dl. Preferably, correction should beperformed when it is within a range from 10 to 400 mg/dl, and morepreferably, from 10 to 250 mg/dl.

The ambient temperature is set so as to perform correction when it iswithin a range from 5 to 45° C. Preferably, correction should beperformed when it is within a range from 10 to 40° C., and morepreferably, from 15 to 35° C.

When the analyte is blood, it is set to perform correction when thehematocrit value is within a range from 0 to 70%. Preferably, correctionshould be performed when the hematocrit value is within a range from 15to 70%, and more preferably, from 30 to 70%. Calculation of thehematocrit value is preferably executed before the calculation of theglucose concentration (step S207), and more preferably, the glucoseconcentration should be corrected based on the calculated hematocritvalue. Further, the hematocrit value is not necessarily measured in thebiosensor. For example, the hematocrit value may be previouslycalculated by a large-size measurement apparatus and inputted to themeasurement device.

When it is judged in step S208 that correction should be performed, theamount of correction for the measurement result of the glucoseconcentration in the blood that is applied to the biosensor 30 isobtained from the correction table shown in FIG. 4, and the measurementresult is corrected (step S209). The corrected value is displayed on thedisplay part of the measurement device 110 a as the concentration ofglucose included in the blood as the analyte (step S210). If it isjudged from the time T that the reliability of the measurement result islow, an error display may be performed without displaying themeasurement result, or it may be displayed that the reliability of themeasurement result is low.

On the other hand, when it is judged in step S208 that correction is notnecessary, the operation goes to step S210 and the value calculated instep S207 is displayed as it is. In this first embodiment, it is judgedthat correction is not necessary when the time T exceeds 20 sec.

By performing the aforementioned operation, more reliably correction canbe carried out.

As described above, in the liquid sample measurement method andapparatus of this first embodiment, the time T from when the biosensor30 is inserted in the measurement device 110 a to when blood is appliedto the sensor 30 is measured, and the measurement result of the glucoseconcentration in the blood applied to the biosensor 30 is correctedbased on the measurement time T. Therefore, adverse effect of fingertipheat on the measurement result is avoided, and a highly-precisemeasurement result can be obtained even when the measurement time isshort. Further, a highly-precise measurement apparatus can be realizedat low cost without newly providing a temperature sensor for measuringthe temperature of the biosensor 30 itself.

Further, in this first embodiment, it is possible to dramaticallyimprove the measurement precision by adopting not only the measured timeT but also the glucose concentration, the hematocrit value, the ambienttemperature and the like as the correction parameters for determiningthe amount of correction for the measurement result of the glucoseconcentration in blood that is applied to the biosensor 30.

Embodiment 2

Hereinafter, a biosensor measurement system according to a secondembodiment of the present invention will be described.

The biosensor measurement system of this second embodiment is configuredso as to correct the ambient temperature on the basis of the time T fromwhen the biosensor is inserted in the measurement device to when theanalyte is applied to the sensor, and perform correction for themeasurement result of the concentration of the specific component in theanalyte that is applied to the biosensor on the basis of the correctedambient temperature.

The configuration of the biosensor measurement system of this secondembodiment is identical to that of the first embodiment shown in FIG. 1.

Hereinafter, the liquid sample measurement method by the biosensormeasurement system of the second embodiment will be described withreference to FIG. 6.

When the biosensor 30 is set in the support part of the measurementdevice 110 a, it is judged whether the biosensor 30 is inserted or notby the switch in the support part. When it is detected that thebiosensor 30 is inserted, the power supply of the measurement device 110a is automatically turned on (step S601). Then, the ambient temperatureis measured by the temperature sensor 120 (step S602), and themeasurement device 110 a goes into the analyte introduction stand-bystate (step S603). The analyte introduction stand-by state is the stateafter starting voltage application from the reference voltage supply 119to the connectors 112 to 114, starting current measurement by thecurrent/voltage conversion circuit 116, and starting measurement of timefrom when the biosensor 30 is inserted to when the analyte is applied tothe sensor 30 using the timer 122.

When the blood as the analyte is applied to the biosensor 30, thecurrent/voltage conversion circuit 116 reads a change in the currentvalue to detect that the analyte is introduced (applied) to the sensor30 (step S604). The count by the timer 122 is completed upon detectingthe analyte introduction (step S605), and the time T from when thebiosensor 30 is inserted in the measurement device 110 a (the analyteintroduction stand-by state) to when the analyte introduction isdetected is calculated (step S606).

Then, whether correction should be performed or not for the temperaturemeasured in step S602 is judged based on the time T calculated in stepS606 (step S607). When it is judged in step S607 that correction shouldbe performed, the operation goes to step S608, wherein the temperaturemeasured in step S602 is corrected and the corrected temperature isregarded as the ambient temperature, followed by step S609. On the otherhand, when it is judged in step S607 that correction is not necessary,the temperature measured in step S602 is regarded as the ambienttemperature, and the operation goes to step S609.

For example, the judgement in step S607 is set such that correctionshould be performed when the time T is within a range from 0.01 to 60sec. Preferably, correction should be performed when the time T iswithin a range from 0.01 to 30 sec, and more preferably, from 0.01 to 20sec. The read interval of the time T is set to every 1 sec. Preferably,it is set to every 0.1 sec, and more preferably, every 0.01 sec.

For example, in the case where the measurement is performed at theambient temperature of 25° C., the amount of correction for the measuredtemperature is +4° C. to correct the ambient temperature to 29° C. whentime T=1.0 (sec), the amount of correction for the measured temperatureis +3° C. to correct the ambient temperature to 28° C. when time T=5.0(sec), and the amount of correction for the measured temperature is +1°C. to correct the ambient temperature to 26° C. when time T=15.0 (sec).On the other hand, since the influence of the fingertip heat on themeasurement result is extremely small when time T=20.0 (sec), it isjudged that correction is not necessary, and the temperature measured instep S602 is adopted as the ambient temperature.

Then, the glucose concentration in the blood that is applied to thebiosensor 30 is calculated (step S609). At this time, the correctionamount is obtained from the temperature correction table stored in theRAM 121 on the basis of the temperature corrected in step S608 when itis judged in step S607 that correction should be performed, or on thebasis of the temperature measured in step S602 when it is judged in stepS607 that correction is not necessary, and correction is performed tothe measurement result of the glucose concentration in the blood that isapplied to the biosensor 30.

The glucose concentration calculated in step S609 is displayed on thedisplay part of the measurement device 110 a as the concentration ofglucose included in the blood as the analyte (step S610).

As described above, in the liquid sample measurement method andapparatus of this second embodiment, the ambient temperature is measuredin addition to measuring the time T from when the biosensor 30 isinserted in the measurement device 110 a to when blood is applied to thesensor 30, and this ambient temperature is corrected based on the timeT, and then the measurement result of the glucose concentration in theblood that is applied to the biosensor 30 is corrected on the basis ofthe corrected ambient temperature. Therefore, adverse effect of thefingertip heat on the measurement result is avoided as in the firstembodiment, and thereby a highly-precise measurement result can beobtained even when the measurement time is short. Further, ahighly-precise measurement device can be realized at low cost withoutnewly providing a temperature sensor for measuring the temperature ofthe biosensor 30 itself.

While in the first and second embodiments the biosensor 30 is anelectrode type sensor, it may be an optical sensor.

While in the first and second embodiments blood glucose is adopted asthe measurement target substance, the measurement target substance isnot restricted thereto, and a biological sample such as cholesterol,triglyceride, lactic acid, uric acid, bilirubin, or alcohol, an ambientsample, or a food sample may be adopted with the same effects asdescribed above.

Embodiment 3

Hereinafter, a biosensor measurement system according to a thirdembodiment of the present invention will be described.

In this third embodiment, blood is used as an analyte, and theconcentrations of glucose and lactic acid as specific components inblood are simultaneously measured in a single sensor.

In the biosensor measurement system of this third embodiment, themeasurement results of the concentrations of the specific components inthe analyte that is applied to the biosensor are subjected tocorrections most suitable for the respective specific components on thebasis of the time T from when the biosensor is inserted in themeasurement device to when the analyte is applied to the sensor.

FIG. 7 is a diagram illustrating the configuration of the biosensormeasurement system of the third embodiment. In FIG. 7, the sameconstituents as those shown in FIG. 1 are given the same referencenumerals.

The biosensor measurement system 100 b of this third embodiment isprovided with a biosensor 700 and a measurement device 110 b. Theexterior appearance of the biosensor measurement system 100 b isidentical to the conventional one shown in FIG. 13, and the measurementdevice 110 b is provided with a display part for displaying themeasurement result, and a support part in which the biosensor isinserted.

The measurement device 110 b is provided with a display part 111,connectors 123, 124, 125, 126, and 127, a switching circuit 115, acurrent/voltage conversion circuit 116, an A/D conversion circuit 117, aCPU 118, a reference voltage supply 119, a temperature sensor 120, a RAM121, and a timer 122.

The connectors 123, 124, 125, 126, and 127 contact a working electrode707 for measuring lactic acid, a working electrode 708 for measuringglucose, a detection electrode 709, a counter electrode 710 formeasuring glucose, and a counter electrode 711 for measuring lacticacid, respectively.

As shown in FIG. 8, the biosensor 700 is obtained by laminating a cover701 having an vent hole 702 in its center, a spacer 703 having anapproximately rectangle-shaped sample supply channel 704 into which theliquid sample applied to a sample application part 700 a is introduced,reagent layers 705 and 706, and an insulating substrate 712.

The reagent layer 705 supports a reagent which enzymatically reacts withlactic acid in the liquid sample. The reagent layer 706 supports areagent which enzymatically reacts with glucose in the liquid sample.The insulating substrate 712 has an electrode layer on its surface,which electrode layer comprises the working electrode 707 for measuringlactic acid, the working electrode 708 for measuring glucose, thedetection electrode 709, the counter electrode 710 for measuringglucose, and the counter electrode 711 for measuring lactic acid.

The biosensor 700 is different from the biosensor 30 in that the twotypes of reagent layers 705 and 706 for lactic acid measurement andglucose measurement are arranged, and lactic acid measurement isperformed by the lactic acid measuring working electrode 707 and thelactic acid measuring counter electrode 711 while glucose measurement isperformed by the glucose measuring working electrode 708 and the glucosemeasuring counter electrode 710, and analyte detections in therespective measurements are performed using the analyte detectionelectrode 709.

Hereinafter, the liquid sample measurement method by the biosensormeasurement system 100 b of this third embodiment will be described.

When the biosensor 700 is set in the support part of the measurementdevice 110 b, whether the biosensor 700 is inserted or not is judged bythe switch in the support part. When it is detected that the biosensor700 is inserted, the power supply of the measurement device 110 b isautomatically turned on (step S801). Then, the ambient temperature ismeasured by the temperature sensor 120 (step S802), and the measurementdevice 110 b goes into the analyte introduction stand-by state (stepS803). The analyte introduction stand-by state is the state afterstarting voltage application from the reference voltage supply 119 tothe connectors 123 to 127, starting current measurement by thecurrent/voltage conversion circuit 116, and starting measurement of timefrom when the biosensor 700 is inserted to when the analyte is appliedto the sensor 30 by the timer 122.

When blood as the analyte is applied to the biosensor 700, thecurrent/voltage conversion circuit 116 reads a change in the currentvalue to detect that the analyte is introduced (applied) into the sensor700 (step S804). The count by the timer 122 is completed upon detectingthe analyte introduction (step S805), and the time T from when thebiosensor 700 is inserted in the measurement device 110 b (the analyteintroduction stand-by state) to when the analyte introduction isdetected is calculated (step S806).

Then, the glucose concentration (step S807) and the lactic acidconcentration (S808) in the blood that is applied to the biosensor 700are calculated. At this time, correction amounts are obtained from thetemperature correction tables stored in the RAM 121 on the basis of theambient temperature measured in step 802, and corrections are performedfor the measurement results of the glucose concentration and the lacticacid concentration in the blood that is applied to the biosensor 700. Atthis time, the corrections are desirably performed using a temperaturecorrection table for correcting the glucose concentration and atemperature correction table for correcting the lactic acidconcentration. This is because the influence of the ambient temperaturediffers depending on the measurement target substance.

Thereafter, whether or not corrections should be performed to theglucose concentration value calculated in step S807 and to the lacticacid concentration value calculated in step S808 are respectively judgedon the basis of the time T calculated in step S806 (step S809, stepS810). In these judgments, it is preferable to provide the judgmentalstandards for the glucose concentration measurement and the lactic acidconcentration measurement, respectively. For example, the respectiveparameters are previously set within the same ranges as in the firstembodiment for the glucose concentration measurement, while it ispreviously set that correction should be performed when the respectiveparameters are within the ranges described below for the lactic acidconcentration measurement.

The time T is set so as to perform correction when it is within a rangefrom 0.01 to 60 sec. Preferably, correction should be performed whentime T is within a range from 0.01 to 30 sec, and more preferably, from0.01 to 20 sec. The read interval of the time T is set to every 1 sec.Preferably, it is set to every 0.1 sec, and more preferably, every 0.01sec.

The lactic acid concentration is set so as to perform correction when itis within a range from 5 to 300 mg/dl. Preferably, correction should beperformed when the lactic acid concentration is within a range from 5 to200 mg/dl, and more preferably, from 5 to 100 mg/dl.

The ambient temperature is set so as to perform correction when it iswithin a range from 5 to 45° C. Preferably, correction should beperformed when the ambient temperature is within a range from 10 to 40°C., and more preferably, from 15 to 35° C.

When the analyte is blood, it is set to perform correction when thehematocrit value is within a range from 0 to 70%. Preferably, correctionshould be performed when the hematocrit value is within a range from 15to 70%, and more preferably, from 30 to 70%. Calculation of thehematocrit value is desirably performed before calculation of theglucose concentration (process in step S807) and calculation of thelactic acid concentration (process in step S808), and more preferably,the glucose concentration and the lactic acid concentration should becorrected based on the calculated hematocrit value. Also in this case,the corrections are desirably performed using correction calibrationcurves for the glucose concentration and the lactic acid concentration,respectively, as in the case of the temperature correction table. Thisis because the degree of influence by the hematocrit value differsbetween the glucose concentration measurement and the lactic acidconcentration measurement. Further, the hematocrit value is notnecessarily measured by the biosensor 700, and for example, it may bepreviously calculated by a large-sized measurement apparatus and thecalculated value may be input to the measurement device.

When it is judged in step S809 that correction should be performed, anamount of correction for the measurement result of the glucoseconcentration in the blood that is applied to the biosensor 700 isobtained from the correction table shown in FIG. 4 as in the firstembodiment, and the measurement result is corrected (step S811).Further, when it is judged in step S810 that correction should beperformed, an amount of correction for the measurement result of thelactic acid concentration in the blood is obtained from the correctiontable shown in FIG. 10, and the measurement result is corrected (stepS812). The method of calculating the correction amount is identical tothe method described in the first embodiment except that the correctiontable differs. In this way, most suitable corrections can be performedby using the correction tables which have been prepared for the glucoseconcentration measurement and the lactic acid concentration measurement,respectively. This is because the degree of influence by the fingertipheat differs between the glucose concentration measurement and thelactic acid concentration measurement.

The corrected values are displayed on the display part of themeasurement device 110 b as the concentrations of glucose and lacticacid included in the blood as the analyte (step S813, step S814). If itis judged from the time T that the reliability of the measurement resultis unsatisfactory, an error display may be performed without displayingthe measurement result, or it may be displayed that the reliability ofthe measurement result is low.

On the other hand, when it is judged in step S809 that correction is notnecessary, the operation goes to step S813 to display the glucoseconcentration calculated in step S807 as it is. Further, when it isjudged in step S810 that correction is not necessary, the operation goesto step S814 to display the lactic acid concentration calculated in stepS808 as it is. In this third embodiment, it is judged that correction isnot necessary when the time T exceeds 20 sec.

More reliable corrections can be realized by performing theabove-described operations.

FIGS. 11( a) and 11(b) show the measurement result of the glucoseconcentration and the measurement result of the lactic acidconcentration which are obtained by the conventional biosensormeasurement system 20, respectively. The abscissa shows the time T(sec)from when the biosensor 30 is inserted in the measurement device 21 towhen blood is applied to the sensor 30, and the ordinate shows thedegree of divergence(%) from the true value. The measurement wasperformed at the ambient temperature of 25° C. using an analyte having aglucose concentration prepared at 85 mg/dl and a lactic acidconcentration prepared at 50 mg/dl (hematocrit value of 45%). At thistime, the biosensor 30 was inserted in the measurement device 21 by sixdonors having different fingertip temperatures, and the time T up to theapplication of the analyte after the insertion of the sensor 30 wasmeasured within a range from 0.01 to 40 sec.

As can be seen from FIGS. 11( a) and 11(b), the degree of divergencefrom the true value becomes larger as the time T is shorter, and thedegree of influence differs depending on the measurement targetsubstance. That is, the fingertip heat influences the measurementresult, and the influence by the heat differs depending on themeasurement target substance.

On the other hand, in the biosensor measurement system 100 b of thisthird embodiment, the measurement results of the glucose concentrationand the lactic acid concentration in the blood that is applied to thebiosensor 700 (these measurement results are values obtained after thetemperature correction) are respectively corrected using the mostsuitable calibration curves on the basis of the time T from when thebiosensor 700 is inserted in the measurement device 110 b to when theblood is applied to the sensor 700.

In this way, the measurement results of the glucose concentration andthe lactic acid concentration in the blood that is applied to thebiosensor 700 are respectively corrected based on the time T, andthereby the degree of divergence from the true value can be minimizedeven when the time T is within 20 sec as shown in FIGS. 12( a) and12(b), resulting in improved measurement precision.

The numerical values on the correction tables shown in FIG. 10 aremerely examples, and the correction amounts are not restricted thereto.Further, the number of tables is also not restricted to those shown inFIG. 10, and the measurement precision can be more improved as thenumber of tables becomes larger.

As described above, according to the liquid sample measurement methodand apparatus of this third embodiment, the time T from when thebiosensor 700 is inserted in the measurement device 110 b to when bloodis applied to the sensor 700 is measured, and the measurement results ofthe glucose concentration and lactic acid concentration in the bloodthat is applied to the biosensor 700 are corrected based on the measuredtime T, using the correction tables which are most suitable for theglucose concentration and the lactic acid concentration, respectively.Therefore, the influence of the fingertip heat on the measurement resultis avoided, thereby obtaining a highly-precise measurement result evenwhen the measurement time is short. Further, a highly-precisemeasurement apparatus can be realized at low cost without newlyproviding a temperature sensor for measuring the temperature of thebiosensor 700 itself.

While in this third embodiment the biosensor 700 is an electrode typesensor, any measurement method can be similarly adopted so long as themeasurement result is affected by the fingertip heat. For example, itmay be an optical sensor, or a combination of an electrode type sensorand an optical sensor.

Further, while in this third embodiment the glucose concentration andthe lactic acid concentration are described as plural measurement targetsubstances to be measured in a single sensor, the measurement targetsubstances are not restricted thereto. For example, various combinationssuch as glucose and cholesterol, glucose and triglyceride, glucose andhemoglobin A1c, glucose and ketone body, glucose and hematocrit, lacticacid and uric acid, uric acid and bilirubin are considered, and further,biological samples, ambient samples, food samples and the like can alsobe adopted with the same effects as described above. Further, the numberof measurement target items is not restricted to two, and more than twoitems may be adopted.

Furthermore, while in this third embodiment plural measurement targetsubstances are measured in a single biosensor, plural kinds ofbiosensors may be inserted to be used in a single measurement device. Inthis case, for example, the measurement device is made to recognize thekinds of the biosensors by electrode patterns of the biosensors ormanual buttons of the measurement device, and correction tables mostsuitable for the respective biosensors are used, whereby most suitablecorrections can be performed to the measurement items according to therespective types of biosensors, thereby obtaining highly precisemeasurement results as in the first to third embodiments.

It is to be noted that the present invention relates to a biosensormeasurement system comprising a biosensor and a measurement device, andthe biosensor is restricted to one which is directly held by the userand inserted in the measurement device to perform measurement, andtherefore, a cartridge type biosensor is out of the scope of theinvention.

APPLICABILITY IN INDUSTRY

A biosensor measurement system of the present invention can be utilizedas a liquid sample measurement apparatus which is low in cost and hasfavorable measurement precision.

1. A liquid sample measurement method of attaching a biosensor to ameasurement device and measuring the concentration of a specificcomponent in a liquid sample that is applied to the biosensor, includingthe steps of: measuring the time from when the biosensor is attached tothe measurement device to when the liquid sample is applied to thesensor, and performing correction for the measurement result of theconcentration of the specific component in the liquid sample that isapplied to the biosensor, on the basis of the measured time.
 2. A liquidsample measurement method of attaching a biosensor to a measurementdevice and measuring the concentrations of plural specific components ina liquid sample that is applied to the biosensor, including the stepsof: measuring the time from when the biosensor is attached to themeasurement device to when the liquid sample is applied to the sensor,and performing corrections for the respective measurement results of theconcentrations of the plural specific components in the liquid samplethat is applied to the biosensor, on the basis of the measured time. 3.A liquid sample measurement method of attaching plural biosensors ofdifferent types to a measurement device and measuring the concentrationsof specific components in liquid samples that are applied to therespective biosensors, including the steps of: measuring the time fromwhen each of the biosensors is attached to the measurement device towhen the liquid sample is applied to the sensor, and performingcorrection for the measurement result of the concentration of thespecific component in the liquid sample that is applied to thebiosensor, on the basis of the measured time and the type of thebiosensor.
 4. A liquid sample measurement method as defined in claim 1,wherein the amount of correction for the measurement result of theconcentration of the specific component in the liquid sample that isapplied to the biosensor is varied according to the measured time fromwhen the biosensor is attached to the measurement device to when theliquid sample is applied to the sensor.
 5. A liquid sample measurementmethod as defined in claim 4, wherein the amount of correction isreduced when the measured time from when the biosensor is attached tothe measurement device to when the liquid sample is applied to thesensor is long.
 6. A liquid sample measurement method as defined inclaim 1, wherein whether correction should be performed or not for themeasurement result of the concentration of the specific component in theliquid sample that is applied to the biosensor is judged according tothe measured time from when the biosensor is attached to the measurementdevice to when the liquid sample is applied to the sensor.
 7. A liquidsample measurement method as defined in claim 6, wherein said correctionis performed when the measured time from when the biosensor is attachedto the measurement device to when the liquid sample is applied to thesensor is within a specific time period.
 8. A liquid sample measurementmethod as defined in claim 1, wherein the amount of correction for themeasurement result is determined according to the measurement result ofthe concentration of the specific component in the liquid sample that isapplied to the biosensor.
 9. A liquid sample measurement method asdefined in claim 1, wherein the amount of correction for the measurementresult of the concentration of the specific component in the liquidsample that is applied to the biosensor is determined according to theambient temperature at the measurement.
 10. A liquid sample measurementmethod as defined in claim 1, wherein the amount of correction for themeasurement result of the concentration of the specific component in theliquid sample that is applied to the biosensor is determined accordingto a second specific component which exists in the liquid sample and isother than said specific component.
 11. A liquid sample measurementmethod as defined in claim 10, wherein the liquid sample is blood, andthe amount of correction is determined according to the hematocrit valueof the blood.
 12. A liquid sample measurement method of attaching abiosensor to a measurement device and measuring the concentration of aspecific component of a liquid sample that is applied to the sensor,including the steps of: measuring the time from when the biosensor isattached to the measurement device to when the liquid sample is appliedto the sensor, and the ambient temperature at the measurement,correcting the measured ambient temperature on the basis of the measuredtime from when the biosensor is attached to the measurement device towhen the liquid sample is applied to the sensor, and correcting themeasurement result of the concentration of the specific component in theliquid sample that is applied to the biosensor, on the basis of thecorrected ambient temperature.
 13. A liquid sample measurement method asdefined in claim 1, wherein the amount of correction for the measurementresult is determined according to the kind of the liquid sample that isapplied to the biosensor.
 14. A liquid sample measurement apparatushaving a biosensor attached thereto, which measures the concentration ofa specific component in a liquid sample that is applied to thebiosensor, including: a time measurement means for measuring the timefrom when the biosensor is attached to when the liquid sample is appliedto the sensor; and a measurement result correction means for correctingthe measurement result of the concentration of the specific component inthe liquid sample that is applied to the biosensor, on the basis of thetime measured by the time measurement means.
 15. A liquid samplemeasurement apparatus as defined in claim 14, wherein said measurementresult correction means changes the amount of correction for themeasurement result of the concentration of the specific component in theliquid sample that is applied to the biosensor, according to the timemeasured by the time measurement means.
 16. A liquid sample measurementapparatus as defined in claim 15, wherein said measurement resultcorrection means reduces the amount of correction when the time measuredby the time measurement means is long.
 17. A liquid sample measurementapparatus as defined in claim 14, wherein said measurement resultcorrection means judges whether correction should be performed or notfor the measurement result of the concentration of the specificcomponent in the liquid sample that is applied to the biosensor,according to the time measured by the time measurement means.
 18. Aliquid sample measurement apparatus as defined in claim 17, wherein saidmeasurement result correction means performs said correction when thetime measured by the time measurement means is within a specific time.19. A liquid sample measurement apparatus as defined in claim 14,wherein said measurement result correction means determines the amountof correction for the measurement result according to the measurementresult of the concentration of the specific component in the liquidsample that is applied to the biosensor.
 20. A liquid sample measurementapparatus as defined in claim 14 further including a temperaturemeasurement part for measuring the ambient temperature at themeasurement, and said measurement result correction means determiningthe amount of correction for the measurement result of the concentrationof the specific component in the liquid sample that is applied to thebiosensor, according to the ambient temperature measured by thetemperature measurement part.
 21. A liquid sample measurement apparatusas defined in claim 14, wherein said measurement result correction meansdetermines the amount of correction for the measurement result of theconcentration of the specific component in the liquid sample that isapplied to the biosensor, according to a second specific component whichexists in the liquid sample and is other than said specific component.22. A liquid sample measurement apparatus as defined in claim 21,wherein said liquid sample is blood, and said second specific componentis the hematocrit value of the blood.
 23. A liquid sample measurementapparatus as defined in claim 14, wherein said measurement resultcorrection means determines the amount of correction for the measurementresult according to the type of the liquid sample that is applied to thebiosensor.
 24. A liquid sample measurement apparatus having a biosensorattached thereto, which measures the concentration of a specificcomponent in a liquid sample that is applied to the biosensor,including: a time measurement means for measuring the time from when thebiosensor is attached to when the liquid sample is applied to thesensor; a temperature sensor for measuring the ambient temperature atmeasurement; a temperature correction means for correcting the ambienttemperature measured by the temperature sensor, on the basis of the timemeasured by the time measurement means; and a measurement resultcorrection means for performing correction for the measurement result ofthe concentration of the specific component in the liquid sample that isapplied to the biosensor, on the basis of the corrected ambienttemperature.
 25. A liquid sample measurement method as defined in claim2, wherein the amount of correction for the measurement result of theconcentration of the specific component in the liquid sample that isapplied to the biosensor is varied according to the measured time fromwhen the biosensor is attached to the measurement device to when theliquid sample is applied to the sensor.
 26. A liquid sample measurementmethod as defined in claim 3, wherein the amount of correction for themeasurement result of the concentration of the specific component in theliquid sample that is applied to the biosensor is varied according tothe measured time from when the biosensor is attached to the measurementdevice to when the liquid sample is applied to the sensor.
 27. A liquidsample measurement method as defined in claim 2, wherein whethercorrection should be performed or not for the measurement result of theconcentration of the specific component in the liquid sample that isapplied to the biosensor is judged according to the measured time fromwhen the biosensor is attached to the measurement device to when theliquid sample is applied to the sensor.
 28. A liquid sample measurementmethod as defined in claim 3, wherein whether correction should beperformed or not for the measurement result of the concentration of thespecific component in the liquid sample that is applied to the biosensoris judged according to the measured time from when the biosensor isattached to the measurement device to when the liquid sample is appliedto the sensor.
 29. A liquid sample measurement method as defined inclaim 2, wherein the amount of correction for the measurement result isdetermined according to the measurement result of the concentration ofthe specific component in the liquid sample that is applied to thebiosensor.
 30. A liquid sample measurement method as defined in claim 3,wherein the amount of correction for the measurement result isdetermined according to the measurement result of the concentration ofthe specific component in the liquid sample that is applied to thebiosensor.
 31. A liquid sample measurement method as defined in claim 2,wherein the amount of correction for the measurement result of theconcentration of the specific component in the liquid sample that isapplied to the biosensor is determined according to the ambienttemperature at the measurement.
 32. A liquid sample measurement methodas defined in claim 3, wherein the amount of correction for themeasurement result of the concentration of the specific component in theliquid sample that is applied to the biosensor is determined accordingto the ambient temperature at the measurement.
 33. A liquid samplemeasurement method as defined in claim 2, wherein the amount ofcorrection for the measurement result of the concentration of thespecific component in the liquid sample that is applied to the biosensoris determined according to a second specific component which exists inthe liquid sample and is other than said specific component.
 34. Aliquid sample measurement method as defined in claim 3, wherein theamount of correction for the measurement result of the concentration ofthe specific component in the liquid sample that is applied to thebiosensor is determined according to a second specific component whichexists in the liquid sample and is other than said specific component.35. A liquid sample measurement method as defined in claim 2, whereinthe amount of correction for the measurement result is determinedaccording to the kind of the liquid sample that is applied to thebiosensor.
 36. A liquid sample measurement method as defined in claim 3,wherein the amount of correction for the measurement result isdetermined according to the kind of the liquid sample that is applied tothe biosensor.